If there is one person at a table who orders wine by the bottle, that person may or may not be aware that the wine will not go well with all of the different meals the guests at the table will order. It may even clash with the food.
If you sense that the person ordering the wine is just forcing his or her tastes on others, when that bottle nears completion, you have an opportunity to bring up which wines-by-the-glass will go well with individual food items the guests have ordered.